Get a glass drink dispenser with spigot, available at Pottery Barn and similar stores. www.pottery.barn and search "decorator drink dispenser". People can easily serve themselves and they are quite attractive.

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I would suggest in addition to this, that you freeze some coffee in ice cube trays and add the frozen coffee to the dispenser. That way, the coffee does not get diluted.

My cousin also served iced coffee at a baby shower. She put cold coffee in one of those thermos dispensers that you see used for dispensing hot coffee. She also put out a bottle of vanilla Torani syrup with a pump dispenser and a container of whole milk. All you had to do was fill cup with ice. Add a couple pumps of syrup, some milk or not, then some coffee. It was delicious and easy.